We propose to investigate the initiation of DNA replication and DNA repair processes in phage T4. We also propose to examine the relationship of DNA damage and repair to the major biological phenomenon of aging. In particular, we plan to study the molecular interactions of phage T4 topoisomerase with the site(s) of initiation of DNA replication, as well as with sites of DNA lesions. We expect to determine some of the molecular intermediates in recombinational repair of damaged DNA. We also plan to identify and characterize further gene functions used in the initiation of DNA replication. Finally we expect to critically examine the role of DNA lesions and DNA repair in aging through a detailed review of current literature.